Every elevator installation needs a certain proportion of space in a building depending on the level of traffic. The greater the level of traffic and the higher the building, the more space the elevator installation needs in relation to the usable area of the building.
It is of considerable concern to keep the need for space of an elevator installation as small as possible while the performance or conveying capacity corresponds with the requirements of a building.
There are various approaches to the provision and operation of more than only one elevator cage in an elevator installation, to the arrangement of several parallel elevator shafts of an elevator installation and to the change of shaft of the elevator cages from one elevator shaft to another elevator shaft.
An appropriate example can be inferred from the document JP 04341479 A, Patent Abstracts of Japan, with the title “Double Cage Elevator”. According to this Japanese patent application an elevator shaft is proposed in which two elevator cages move in opposite directions. Provided in the middle region of the elevator shaft is a diversion zone which has the form of a widening of the elevator shaft and which is to enable the two elevator cages to pass by each other without colliding.
It is a disadvantage of this previously known elevator installation with an elevator shaft with a diversion zone that the diversion zone occupies a relatively large enclosed area in the building structure. Moreover, the outlay on creating such an elevator shaft with a widening is somewhat unfavorable for structural and engineering reasons.
Elevator installations are also known which are equipped with a so-termed double-deck cage for increasing the conveying capacity. The double-deck cage is an elevator cage with two passenger compartments arranged one above the other. Such a double-deck cage has to be loaded/unloaded simultaneously from two stories when it stops in a boarding zone of the elevator installation. The conveying capacity is thus significantly improved. However, it has proved that a double-deck cage is also accompanied by disadvantages. Thus, such an elevator installation is not capable of flexible use, since the entire double-deck cage always has to be transported even when only a smaller amount of conveying capacity is required. Moreover, the deck spacing of the double-deck cage has to take into consideration the spacing of the stories. The spacing between individual stories is frequently not completely uniform, which obliges additional technical measures with the double-deck cage.